Release only if token present

Author: glibas

appveyor.yml

@@ -43,10 +43,12 @@ test: off
 artifacts:
   - path: .\build\stage
 on_success:
-    on:
-      branch: master
-  - git config --global credential.helper store
-  - ps: Add-Content "$env:USERPROFILE\.git-credentials" "https://$($env:NODE_PRE_GYP_GITHUB_TOKEN):[email protected]`n"
-  - git config --global user.email "[email protected]"
-  - git config --global user.name "MatthD"
-  - node-pre-gyp-github publish --release
+  - ps: |
+        if ($env:NODE_PRE_GYP_GITHUB_TOKEN)
+        {
+            git config --global credential.helper store
+            Add-Content "$env:USERPROFILE\.git-credentials" "https://$($env:NODE_PRE_GYP_GITHUB_TOKEN):[email protected]`n"
+            git config --global user.email "[email protected]"
+            git config --global user.name "MatthD"
+            node-pre-gyp-github publish --release
+        }